This document summarizes an expert panel's review of evidence on the effects of physical activity on health outcomes in school-age youth. The panel identified over 850 relevant articles through a systematic search. They found: 1) Most intervention studies showed benefits of 30-45 minutes per day of moderate to vigorous physical activity 3-5 days per week. However, the panel believed greater amounts would be needed for benefits under normal circumstances. 2) The panel concluded that school-age youth should participate in 60 minutes or more per day of moderate to vigorous physical activity from a variety of activities. 3) Physical activity was associated with reduced adiposity, especially for overweight youth, and improved cardiovascular health factors like blood lipid levels and aer

1. ORIGINAL
ARTICLES
EVIDENCE BASED PHYSICAL ACTIVITY FOR SCHOOL-AGE YOUTH
WILLIAM B. STRONG, MD,* ROBERT M. MALINA, PHD,* CAMERON J. R. BLIMKIE, PHD, STEPHEN R. DANIELS, MD, PHD,
RODNEY K. DISHMAN, PHD, BERNARD GUTIN, PHD, ALBERT C. HERGENROEDER, MD, AVIVA MUST, PHD, PATRICIA A. NIXON, PHD,
JAMES M. PIVARNIK, PHD, THOMAS ROWLAND, MD, STEWART TROST, PHD, AND FRANCxOIS TRUDEAU, PHD
Objectives To review the effects of physical activity on health and behavior outcomes and develop evidence-based
recommendations for physical activity in youth.
Study design A systematic literature review identified 850 articles; additional papers were identified by the expert
panelists. Articles in the identified outcome areas were reviewed, evaluated and summarized by an expert panelist. The strength
of the evidence, conclusions, key issues, and gaps in the evidence were abstracted in a standardized format and presented and
discussed by panelists and organizational representatives.
Results Most intervention studies used supervised programs of moderate to vigorous physical activity of 30 to 45 minutes
duration 3 to 5 days per week. The panel believed that a greater amount of physical activity would be necessary to achieve similar
beneficial effects on health and behavioral outcomes in ordinary daily circumstances (typically intermittent and unsupervised
activity).
Conclusion School-age youth should participate daily in 60 minutes or more of moderate to vigorous physical activity that
is developmentally appropriate, enjoyable, and involves a variety of activities. (J Pediatr 2005;146:732-7)
R
ecommendations for appropriate amounts of physical activity for the US
population, including school-age youth, have been developed by several
organizations and agencies.1
Although recent reviews have summarized the
benefits of regular physical activity on the health of youth and its potential for reducing the
incidence of chronic diseases that are manifested in adulthood,2-5
a more systematic
approach is indicated. This report presents results of a systematic evaluation of evidence
dealing with the effects of regular physical activity on several health and behavioral
outcomes in US school-age youth, with the goal of developing a recommendation for the
amount of physical activity deemed appropriate to yield beneficial health and behavioral
outcomes.
METHOD
Under a contract with the Divisions of Nutrition and Physical Activity and
Adolescent and School Health of the Centers for Disease Control and Prevention and the
Constella Group, an expert panel was convened to review and evaluate available evidence
on the influence of physical activity on several health and behavioral outcomes in youth
aged 6 to 18 years. The co-chairs of the panel selected panelists on the basis of expertise in
specific areas: adiposity, cardiovascular health (lipids and lipoproteins, blood pressure, the
metabolic syndrome, type 2 diabetes mellitus, cardiovascular reactivity, heart rate
variability, inflammation, and cardiovascular fitness), asthma, several domains of mental
health (self-concept, anxiety, depression), academic achievement, injury associated with
physical activity, and musculoskeletal health (bone mineral, muscular strength, and
endurance). The epidemiology and tracking of physical activity and overweight in youth
HDL-C High-density lipoprotein cholesterol level
LDL-C Low-density lipoprotein cholesterol level
MS Metabolic syndrome
732
From the Department of Pediatrics, Med-
ical College of Georgia, Augusta, Georgia;
Tarleton State University, Stephenville,
Texas; Department of Kinesiology, McMas-
ter University, Hamilton, Ontario, Canada;
Department of Exercise Science, University
of Georgia, Athens, Georgia; Children’s
Hospital Medical Center, Cincinnati, Ohio;
Department of Pediatrics, Adolescent and
Sports Medicine, Baylor College of Medicine,
Houston, Texas; Department of Family
Medicine and Community Health, Tufts
University School of Medicine, Boston,
Massachusetts; Department of Health and
Exercise Science, Wake Forest University,
Winston-Salem, North Carolina; Depart-
ment of Kinesiology, Michigan State Univer-
sity, East Lansing, Michigan; Pediatric
Cardiology, Baystate Medical Center,
Springfield, Massachusetts; Department of
Kinesiology, Kansas State University, Man-
hattan, Kansas; Departement des Sciences
de l’Activite Physique,Universite´ du Quebec
a` Trois-Rivie`res, Trois-Rivie`res, Quebec
City, Canada.
*Contributed equally to this work.
Submitted for publication Sep 9, 2004; last
revision received Nov 29, 2004; accepted
Jan 26, 2005.
Reprint requests: William B. Strong, MD,
3209 Huxley Dr, Augusta, GA 30909.
E-mail: wstrong003@comcast.net.
0022-3476/$ - see front matter
Copyright ª 2005 Elsevier Inc. All rights
reserved.
10.1016/j.jpeds.2005.01.055
See editorial, p 719.

2. were also reviewed because of their public health implications,
but are not included in this report.
Literature Search
Databases (PubMed, ERIC, PsycINFO, 1980 to the
present) were searched for publications in English that were
related to physical activity and specific outcomes in youth.
Approximately 1220 abstracts were reviewed, and >850 articles
were provided to the respective panelists. Articles not
identified in the bibliographic searches were added by several
panelists.
Evaluation of Articles
The panelists systematically evaluated and abstracted
relevant articles for each outcome. This information was
abstracted for each report: complete citation, study design,
characteristics of the study population, measure of physical
activity, statistical analyses, outcome measures, main findings,
and evidence for dose-response effects. The co-chairs and
panelists developed conceptual definitions and inclusion and
exclusion criteria for each of the outcomes. On the basis of the
review of reports, each expert provided a summary of the
evidence for strength (strong [>60% of studies reviewed],
moderate [30%-59% of studies], weak [<30% of studies]) and
direction (positive, null, negative) of physical activity effects
on each health and behavioral outcome.
Meeting Format
A meeting of the panel and representatives of major
organizations and agencies with interests in physical activity
and health of youth was convened in January 2004. The 2-day
meeting was designed and convened for maximum input from
the expert panelists and individuals representing the invited
organizations and agencies (Appendix). Panel members gave
presentations summarizing the evidence for an assigned
outcome; each presentation was followed by an open discus-
sion. The process of developing physical activity recom-
mendations was then discussed among all participants.
Subsequently, the co-chairs and panelists met to develop a
recommendation for physical activity for school-age youth in
the context of the strength of evidence available for each health
and behavioral objective.
RESULTS
Evidence pertaining to the influence of physical activity
on each health and behavior outcome in youth is summarized
in Table I; available online at http://www.us.elsevierhealth.
com/jpeds.
Normal Weight, Overweight, and Obesity
Much of the evidence dealing with adiposity and
cardiovascular outcomes is based on subjects classified as
overweight or obese. Current criteria are based on age- and
sex-specific cut-points of the body mass index (BMI, kg/m2
).
In the context of national US surveys, a BMI >85th and <95th
percentile is defined as ‘‘risk of overweight,’’ and a BMI $95th
percentile is defined as overweight. The labels ‘‘overweight’’
and ‘‘obesity,’’ respectively, are often used in the literature. A
BMI >5th and #85th percentile is considered normal weight.
Criteria for overweight and obesity, however, varied
among studies considered (eg, weight >20% of that expected
for height [relative weight], estimated percent fat >25% in
boys and >30% in girls, triceps skinfold >85th age- and sex-
specific percentiles, and BMI >85th, >90th
, or >95th age- and
sex-specific percentiles). Subjects who were normal weight
had weight, percent fat, skinfold thickness, or BMI below the
cut-points. Designation of subjects as overweight/obese or
normal weight was accepted as described in the respective
reports.
Adiposity
Cross-sectional and longitudinal observational studies
suggest that youth of both sexes who participate in relatively
high levels of physical activity have less adiposity than less
active youth.6-17
Experimental studies of overweight boys and
girls involved in systematic physical activity interventions
provide more specific information about the influence of
physical activity on adiposity. Programs of moderately intense
exercise 30 to 60 minutes in duration, 3 to 7 days per week
lead to a reduction in total body and visceral adiposity in
overweight children and adolescents.18-20
However, such
programs do not influence the percentage of body fat in
normal weight children and adolescents.20-24
Limited evi-
dence indicates that more intensive and longer sessions (>80
minutes/day) are more successful in reducing percentage
fatness in normal weight boys and girls.6,25
The results suggest
that relatively greater amounts of vigorous physical activity
may be needed to have a beneficial effect on adiposity in
normal weight youth.
Cardiovascular Health
Many indicators of cardiovascular health cluster with
overweight and adiposity, and this should be noted in
evaluating potential effects of physical activity.
METABOLIC SYNDROME. Many studies view the metabolic
syndrome (MS) as a clustering of risk factors. A proposed
definition of the MS for adolescents is based on abdominal
obesity (waist circumference >90th percentile), triglycerides
($110 mg/dL), blood pressure (>90th percentiles for age, sex,
height), fasting glucose ($110 mg/dL), and reduced high-
density lipoprotein cholesterol level (HDL-C; #40 mg/dL).26
Few studies have evaluated the impact of physical activity on
the MS in youth.
Obese adolescent boys with the MS have lower exercise
performance (exercise duration with a multistage treadmill
protocol) than obese boys without the MS.27
Adolescents with
type 2 diabetes mellitus, in addition to being obese, report no
or very little habitual physical activity.28
In overweight
children, exercise successfully reduced triglyceride and insulin
levels in a randomized trial,29
wheras a 40-minute program of
Evidence Based Physical Activity For School-Age Youth 733

3. moderate to vigorous physical activity 3 times/week improved
some aspects of the MS (triglyceride level, insulin level,
adiposity).30
Several studies show improvement in elements of
the MS in association with physical activity in obese and non-
obese youth,31-36
but the amount of activity necessary to
prevent or treat the MS is not specified.
LIPIDS AND LIPOPROTEINS. Relationships between physical
activity and total cholesterol, HDL-C, low-density lipopro-
tein cholesterol (LDL-C), and triglyceride levels are generally
weak in observational studies. The results suggest a beneficial
effect of physical activity on HDL-C and triglyceride levels,
but no consistent effect on total cholesterol or LDL-C
levels.10,14,17,24,30,36-49
Two studies, however, indicate a null
effect of physical activity on lipid and lipoprotein levels.50,51
The latter more likely applies to youth who entered a study
with relatively normal values. Results of studies relating lipid
and lipoprotein levels to cardiovascular (aerobic) fitness are
inconsistent and do not indicate a significant association.20,52-57
Intervention studies, including clinical or school-based trials
(randomized and non-randomized), show a weak beneficial
effect on HDL-C and triglyceride levels, but not on total
cholesterol or LDL-C levels.25,58-60
School-based interven-
tions have not been effective in improving lipid and lipopro-
tein levels.34,61
Allowing for variation in the available data, it appears
that a minimum of 40 minutes of activity per day, 5 days per
week for 4 months is required to achieve improvement in lipid
and lipoprotein levels, primarily increased HDL-C and
decreased triglyceride levels. This implies the need for a
sustained amount of moderate to vigorous physical activity on
a regular basis to induce and maintain the beneficial effect.
The role of weight loss in mediating the effect of activity on
lipid and lipoprotein levels has not been studied in youth.
BLOOD PRESSURE. Little evidence supports the efficacy of
or need for exercise training to reduce blood pressure in
normotensive youth. A meta-analysis62
and comprehensive
review63
indicate no clear association between physical activity
and reduction of blood pressure in normotensive youth.
Limited studies of youth with systemic hypertension show a
beneficial effect of aerobic activity programs of 12 to 32 weeks
duration on blood pressure64-66
Strength training after an
aerobic intervention prevents the return of blood pressure
to pre-intervention levels in hypertensive adolescents.67
However, an 8-week strength training program by itself has
no influence on blood pressure in hypertensive youth.68
Overall, data suggest that a physical activity intervention with
a duration (at least 30 minutes), frequency (3 times/week), and
intensity sufficient to improve aerobic fitness (approximately
80% of maximal heart rate) can be in reducing blood pressure
in youth with mild essential hypertension. Continued physical
activity is necessary to maintain the beneficial effect.
OTHER CARDIOVASCULAR VARIABLES. Studies of physical ac-
tivity in relation to hemostasis (fibrinogen),30,69-73
inflamma-
tion (high sensitivity C-reactive protein),72,74,75
and
endothelial function76-78
are inconclusive, but experimental
studies indicate a beneficial effect of activity on cardiovascular
autonomic tone.56,79
CARDIOVASCULAR FITNESS (AEROBIC FITNESS). Correlational
studies indicate low-to-moderate positive relationships be-
tween physical activity and maximal and submaximal in-
dicators of aerobic fitness. Comparisons of habitually active
and less-active children and adolescents show better levels of
aerobic fitness in the former.15,80-97
Experimental training
studies with youth 8 years and older indicate improvements
in aerobic fitness.21,24,34,58,61,64,98-109
Successful programs
ordinarily involve continuous vigorous activity (eg, 80%
of maximal heart rate) for >30 minutes at least 3 days per
week.110,111
Change with systematic training averages ap-
proximately 10% (3-4 mL/kg/min).
Asthma
Comparisons of population-based and convenience
samples of youth with asthma give inconsistent results.
Physical activity levels are higher,112,113
lower,114
or not
different112,115-117
in asthmatic compared with non-asthmatic
youth. However, higher levels of activity are associated with
greaterreportingofasthma115
orrelatedsymptoms(eg,whistling,
wheezing116
) in asthmatic youth. Some,117-119
but not all,120-122
studies indicate lower levels of aerobic and anaerobic fitness
in youth with asthma. Risk of developing asthma may be
associated with overweight in boys123
and girls.124
Controlled
aerobic programs (2-3 sessions/week for at least 6 weeks)125-128
result in improved aerobic and anaerobic fitness in youth with
asthma, but are not associated with systematic improvements
in pulmonary function126,128,129
or exercise-induced broncho-
constriction.126-128
Mental Health
Indicators of mental health in youth were delimited to
anxiety, depression, and self-concept. There are too few studies
of physical activity and other important aspects of mental
health, such as perceived stress,130-132
emotional distress,133-134
and perceived vigor or exhaustion.133,135
Moreover, the dearth
of prospective population cohort studies136,137
and randomized
controlled trials138
limits conclusions about causality in results
that are derived mainly from cross-sectional and quasi-
experimental studies.
ANXIETY AND DEPRESSION. Cross-sectional studies suggest
weak positive associations between physical activity and lower
scores on scales of anxiety132,139-141
and depression symp-
toms,130,132,141-147
whereas quasi-experimental studies show
strong positive influences of physical activity and improve-
ment on measures of anxiety132,135
and depression symp-
toms.132,135,148-150
The influence of physical activity on anxiety
and depression symptoms varies with mode of activity.
SELF-CONCEPT. Self-concept refers to the perception of
self, whereas self-esteem refers to the value placed on one’s
734 Strong et al The Journal of Pediatrics June 2005

4. self-concept. Self-concept comprises several domains—
academic and non-academic, social and emotional, and phys-
ical (sport competence, strength or endurance, appearance).
The structure of self-concept changes with age and becomes
more clearly differentiated in the transition into puberty
and during adolescence. Cross-sectional studies suggest a
moderately positive association between physical activity
and physical self-concept, but weak positive associations
between physical activity and global, social, and academic
self-concept.133,139,140,143,145,151-162
Quasi-experimental stud-
ies135,149,150,163-188
indicate strong positive effects of physical
activity on physical (sport competence) and global self-concept
and weaker positive effects on social and academic self-
concept. The influence of physical activity on self-concept may
be mediated by mode of activity, with beneficial effects
associated with aerobics, aerobics combined with strength/
flexibility activities, dance, perceptual-motor, and cognitive
behavioral modifications to augment physical activity.
Although sport activities are positively associated with global
self-concept, they have the potential for negative influence.
Coaching and teaching styles are particularly relevant to the
self-concept in organized sport189
and physical education.190
Academic Performance
Indicators of academic performance include grade point
average, scores on standardized tests, and grades in specific
courses; measures of concentration, memory, and classroom
behaviors are indirect estimates. The addition of physical
education to the curriculum results in small positive gains in
academic performance.191-193
The quasi-experimental data
also suggest that allocating more curricular time to programs of
physical activity does not negatively affect academic achieve-
ment, even when time allocated to other subjects is reduced.194
Some results also suggest a relative increase in academic
performance per unit of time.194,195
Cross-sectional observa-
tions show a positive association between academic perfor-
mance and physical activity142,196-199
and physical fitness.200
Physical activity has a positive influence on concentration and
memory201-209
and on classroom behavior.194
Mechanistic
studies of cognitive function also suggest a positive effect of
physical activity on intellectual performance.210
Injuries
Children and adolescents incur injury in physical
activities associated with recreation, free play, organized and
unorganized sport, and physical education. Most data are case
series based on convenience samples from emergency depart-
ments or sports medicine clinics. Other data are from accident
reports, insurance records, interviews, and retrospective
questionnaires. Variation in definition of injury, inadequate
exposure data, and lack of description of the population at risk
limits the value of much of the published research in drawing
valid conclusions about the risks of injury to children and
adolescents associated with a given physical activity.211
Descriptive longitudinal studies of injury in several high
school sports are an exception.212,213
These studies have a
known denominator, relatively accurate exposure data, imme-
diate access to treatment by an athletic trainer, and a well-
designed data collection system.
Although limited, information on injuries related to
physical education classes suggests that the injury rate is nearly
0 during 20-minute sessions held 3 times/week,214-217
whereas
the prevalence of injury in a supervised after school program is
low, 0.0016 per student hour.218
Musculoskeletal Health and Fitness
MUSCULAR STRENGTH AND ENDURANCE. Although muscular
strength and endurance were not among the primary health
outcomes initially examined, panel members recommended
inclusion because they are important components of physical
fitness. Correlational studies and cross-sectional comparisons
give equivocal results relating physical activity to indicators of
muscular strength and endurance,81,94,219-225
but longitudinal
studies of adolescents indicate a positive influence of habitual
physical activity on upper body muscular endurance.81,220,223
Experimental studies of resistance training 2 or 3 times per
week (with a day of rest between training sessions) show
improvements in muscular strength and endurance during
childhood and adolescence.226-241
Most studies focus on pre-
adolescent children, and strength gains are not associated with
muscular hypertrophy.230,232,237,241
Muscular hypertrophy in
association with gains in strength with resistance training
occurs in adolescent boys,242
but data for adolescents of both
sexes are limited.
BONE MINERAL. The tensile and compressive forces associ-
ated with muscular contractions during weight-bearing activ-
ities and specialized exercises such as strength/resistance
training have a favorable influence on skeletal tissue. Case
studies,243,244
correlational studies,245-252
retrospective studies
of activity in childhood in relation to bone mass in
adulthood,253-259
comparisons of habitually active and inactive
children and adolescents,260-266
and comparisons of elite
young athletes with less active youth267-281
indicate a bene-
ficial effect of physical activity on skeletal health. The
osteogenic influence of physical activity is generally site-
specific and related to local mechanical strains. The benefits
are reflected in bone mineral content, bone mineral density,
and bone mineral apparent density. Prospective studies of
children with varying levels of current or past physical
activity,282-287
and experimental studies give similar results
in pre-pubertal boys and in girls who were either prepuber-
tal215,257,288-292
or in the early stages of puberty.216,293-295
The
experimental studies generally involve programs of 10 to 60
minutes duration of moderate to high-strain activity (impact,
weight bearing) for 2 to 3 or more days per week. The benefits
are not as clearly established for adolescents214,295,296
in later
stages of puberty (primarily girls).
DISCUSSION
Discussions of the benefits of physical activity for youth
are often framed in the context of the future health status of
Evidence Based Physical Activity For School-Age Youth 735

5. the individual. It is also important to consider physical activity
as it relates to the multiple demands of childhood and
adolescence associated with physical growth, biological mat-
uration, and behavioral development. These processes vary
considerably among individuals, occur simultaneously and
interact, and provide the backdrop against which youth
evaluate their own status among peers, especially during
adolescence. This backdrop has implications for many
decisions youth make, including those about physical activity.
Evidence-based data are strong for beneficial effects of
physical activity on musculoskeletal health, several compo-
nents of cardiovascular health, adiposity in overweight youth,
and blood pressure in mildly hypertensive adolescents.
Evidence is adequate to make informed judgments about the
beneficial effects of physical activity on lipid and lipoprotein
levels and adiposity in normal weight children and adolescents,
blood pressure in normotensive youth, other cardiovascular
variables, self-concept, anxiety, and depression symptoms, and
academic performance. A definition of the MS for youth is not
yet firmly established. However, the association between the
MS and adiposity, lipid and lipoprotein levels, and blood
pressure suggests that regulation of overweight through
physical activity may have a beneficial effect on components
of the syndrome.
Recommendations
School-age youth should participate every day in 60
minutes or more of moderate to vigorous physical activity that
is enjoyable and developmentally appropriate. Interventional
studies indicate specific amounts of physical activity necessary
for beneficial changes in the skeletal health, aerobic fitness,
and muscular strength and endurance of youth, and in
adiposity in youth who are overweight (Table). Activity
protocols varied somewhat among studies, but most used
programs of continuous moderate to vigorous activities for
30 to 45 minutes duration for 3 to 5 days per week. It is
reasonable, however, to expect that the amount of physical
activity necessary to achieve similar or greater beneficial effects
in the context of ordinary daily activities, which are typically
intermittent, would be substantially more than indicated in
controlled experimental conditions. This is generally consis-
tent with rationale for prior recommendations.4
Moreover,
allowing for inter- and intra-individual differences in physical
activity and in response to physical activity among free-living
children and adolescents, 60 minutes or more of moderate to
vigorous physical activity on a daily basis is consistent with
desired health and behavioral outcomes.
Physical activities of children and adolescents vary with
age, type of exercise, and setting. Physical activity begins in
infancy with pushing up, turning, crawling, and eventually
walking, and it progresses to more complex activities as
neuromuscular control develops. Basic movement patterns
develop during preschool ages and are the foundation for a
wide range of physical activities at later ages. With growth,
maturation, and experience, basic movements are integrated
and coordinated into more specialized and complex movement
skills that characterize the free play, games, sports, and other
activities of school-age youth. Guided instruction and super-
vised practice, specifically by qualified teachers, coaches, and
others who work with children, are important in learning
movement skills. Types and contexts of activities are variable
and change with age during childhood and adolescence.
Activities of children aged 6 to 9 years are largely anaerobic (as
in non-sustained activities or games such as ‘‘tag’’), and they
help the child learn basic and more specialized motor skills. As
youth move into the pubertal transition (about age 10-14
years, earlier in girls than in boys), these skills are incorporated
into a variety of individual and group activities and many
organized sports. Mature structure and function are ap-
proached or attained in late adolescence (age 15-18 years), so
that physical activity programs can be more structured.
Recommended priorities for physical activities during
childhood and adolescence relative to the development of
skills and to behavioral, health, and fitness benefits are
schematically illustrated in the Figure. During the preschool
and early school ages, general movement activities develop
movement patterns and skills (dashed line in Figure). As these
basic movements become established and skills improve,
health, fitness, and behavioral components of physical activ-
ities increase in importance (solid line in Figure). Health-
related activities include those that emphasize cardiovascular
and muscular endurance and muscular strength and those that
involve weight bearing. The setting of physical activity is
especially important in achieving positive behavioral out-
comes. Although there is less emphasis on the development of
motor skills during adolescence, refinement of those skills is
important and new movement skills can be learned and can
contribute to a physically active lifestyle.
Activities are generally classified as low, moderate,
and vigorous intensity on the basis of METs (metabolic
Figure. Changing emphasis of physical activity during childhood
and adolescence. The figure is modified after R. M. Malina. Fitness
and performance: adult health and the culture of youth, new
paradigms? In: R. J. Park and M. H. Eckert, editors. New
possibilities, new paradigms? (American Academy of Physical
Education Papers No. 24). Champaign, IL: Human Kinetics
Publishers; 1991. p. 30-8.
736 Strong et al The Journal of Pediatrics June 2005

6. equivalents for specific activities on the basis of the ratio of
activity to resting energy expenditure). Tables of MET values
for a variety of activities based largely on measurements in
adults are available.297
Because exercise energy expenditure per
unit of body mass is higher in children and adolescents than in
adults,298
these MET values have limitations. Nevertheless,
moderate-to-vigorous activities require about 5 to 8 METs,4
and such intensity is needed to derive most health benefits.
Brisk walking, bicycling, and active outdoor playing ordinarily
reach this criterion.
The recommended 60 minutes or more of physical
activity can be achieved in a cumulative manner in school
during physical education, recess, intramural sports, and
before and after school programs. In this regard, the Centers
for Disease Control recommends daily quality physical
education from kindergarten through grade 12. Both physical
education and recess afford opportunities to achieve the daily
physical activity goal without any evidence of compromising
academic performance. Opportunities to influence youth
participation in physical activities are readily available at
home and school, as well as in community and health care
settings.
Physical inactivity is a strong contributor to overweight.
Sedentary activities such as excessive television viewing,
computer use, video games, and telephone conversations
should be discouraged. Reducing sedentary behaviors to 2
hours per day is important to increasing physical activity and to
health.
The decline in physical activity during adolescence is of
special concern.299-301
Data from several European countries
highlight the importance of involvement in community-based
sport clubs during adolescence as an important predictor of
physical activity in adolescence.302-306
Restoration of intra-
mural sport programs and expansion of the school day for such
programs in middle and high schools may provide opportu-
nities for all students to be physically active.
For youth who have been physically inactive, an
incremental approach to the 60-minute goal is recommended.
Increasing activity by 10% per week, an approach used in
athletic training, appears to be acceptable and achievable.
Attempting to achieve too much too rapidly is often coun-
terproductive and may lead to injury.
Risk of overweight307
and sedentary behavior308
are
increasingly evident in children aged 2 to 5 years, which has
implications for subsequent ages. It is important to promote
physical activity and limit the amount of physical inactivity
beginning with the preschool child. The family unit, the
pediatric community, day care centers, and preschools are
important contributors to encouraging healthy behaviors.
Children live at home and receive their health care in a variety
of settings, including a pediatrician or family practitioner’s
office, clinics, and public health facilities. The child’s health
care providers should routinely screen for overweight and
inactivity and counsel parents and other care givers about the
health risks of overweight and the health benefits of physical
activity, not only for the child, but also for the parents. At
home, in day care, and in preschool, children should be
regularly encouraged to be active and to explore. The amount
of time that they are restrained from being active should be
minimized. Two recent sets of guidelines for the promotion of
physical activity among youth are excellent sources of infor-
mation on this topic.309,310
Physicians are important in this
process and should be strong advocates of a physically active
lifestyle for youth at home and in schools and communities.
CONCLUSIONS
Increasing the level of habitual moderate- to vigorous-
intensity physical activity in youth is a health promotion and a
disease-prevention strategy. Sedentary youngsters should
progress toward the recommended level of physical activity
gradually. The recommendations are consistent with presently
available scientific evidence and are also in general accord with
recommendations promoted by governmental agencies4,311,312
and professional organizations.3,313,314
APPENDIX
American Cancer Society; American Academy of
Kinesiology and Physical Education; American Diabetes
Association; American Heart Association; American College
of Sports Medicine; American Academy of Pediatrics; Centers
for Disease Control and Prevention, National Association for
Sport and Physical Education; National Cancer Institute;
National Heart, Lung and Blood Institute; National Institute
of Arthritis and Musculoskeletal and Skin Diseases; National
Institute of Child Health and Human Development; National
Institute of Diabetes and Digestive and Kidney Diseases;
National Center for Health Statistics; Robert Wood Johnson
Foundation; US Department of Agriculture; US Department
of Health and Human Services, Office of Public Health
Science; and the US Department of Health and Human
Services, Office of Disease Prevention and Health Promotion,
President’s Council on Physical Fitness and Sports.
References available online at http://www.us.
elsevierhealth.com/jpeds.
Evidence Based Physical Activity For School-Age Youth 737